The invention relates to distancing elements or units in general, and more particularly to improvements in adjustable distancing units. Still more particularly, the invention relates to improvements in distancing units wherein threaded components cooperate in such a way that the length of the unit can be varied in response to rotation of mating externally and internally threaded components relative to each other and that the mating components can be releasably held in selected axial positions relative to each other.
It is already known to assemble a variable-length distancing unit from a standard nut and a hollow tubular screw or bolt whose external thread mates with the internal thread of the nut. The lower end of the screw or bolt (hereinafter called bolt) is provided with a flange serving as an abutment for a standard resilient washer. The just described distancing unit further comprises a sheet metal insert which is positioned between the washer and the nut and serves to prevent uncontrolled changes in the angular (and hence axial) position of the nut relative to the bolt. The thickness (axial length) of the nut is minimal and the greatest difference between the maximum and minimum lengths of the distancing unit is not more than 40 percent of overall axial length of the nut. The negligible adjustability of axial length of the just outlined distancing unit will be readily appreciated by considering that, when using a bolt with a thread whose dimensions are M 30.times.1.5 mm, the maximum range of adjustability of axial length of the distancing unit does not exceed 3 mm. Such minimal adjustability might suffice to compensate for certain unevennesses, manufacturing tolerances and/or inaccurate assembly but is far from being satisfactory or sufficient for a number of important applications. By way of example only, if an electric motor having a power output of up to 7.5 kilowatts is used to transmit torque to the input element of a transmission by resorting to a belt drive, the distance between the axis of rotation of the input element of the transmission and the axis of rotation of the output element of the motor will vary by up to 20 mm in order to account for initial adjustments as well as to compensate for unavoidable slackening of the belt or belts after certain periods of use. Adjustments of such magnitude cannot be carried out by resorting to heretofore known distancing units including those described hereinbefore.